Check-in counters of Irish Ryanair airline are unstaffed at the Hahn airport, western Germany, Friday, Aug. 10, 2018 when several flights were cancelled due to a strike of pilots. (Thomas Frey/dpa via AP)

Passenger walk through the empty departure hall of the Schoenefeld airport near Berlin Friday, Aug. 10, 2018 when several flights of Irish Ryanair airline had been cancelled due to a strike of pilots. (Bernd Settnik/dpa via AP)

Aircraft of Irish Ryanair airline stand on the tarmac of the Hahn airport, western Germany, Friday, Aug. 10, 2018 when several flights were cancelled due to a strike of pilots. (Thomas Frey/dpa via AP)